Various type of curable epoxy resin compositions have been proposed and employed in many fields, especially adhesives because of the good adhesive performance of the epoxy resin compositions. For the adhesives, a curable epoxy resin composition which comprises an epoxy resin and an aromatic polyamine is mainly used because of low water absorption.
The epoxy resin composition, however, is requested to be heat-cured to obtain strong adhesive strength. The composition can be cured at ambient temperature, but it takes a relatively long time. The composition which has been cured at ambient temperature has poor adhesive strength under shear. The epoxy resin composition, accordingly, is not completely satisfied and used in limited fields.
In order to improve the adhesive strength under shear, it is proposed that a polyfunctional acrylate, such as polyethyleneglycol diacrylate, is formulated into the epoxy resin composition. The new formulation adversely increases water absorption and makes water resistance poor, thus being insufficient for adhesives.